It is known that the correction of the myopia of a wearer of glasses results, in the long term, in an increase in the degree of the myopia. Such an aggravation of the myopia is seen in particular in children.
It is attributed to an ophthalmic correction which is adapted for the observation of a distant object by using the central part of the retina, but which is too great for lateral parts of this object, the images of which are formed in the peripheral area of the retina. The foveal vision, or central vision, corresponds to the observation of the object with the central part of each retina, which is called the fovealar area. The lateral parts of the observed object, which are imaged by light rays entering obliquely into the eye, correspond to the peripheral vision of the wearer. Those skilled in the art then speak of overcorrection of the myopia in these peripheral vision conditions. In practice, by using the lens of glasses whose optical power is adapted for the far vision and the foveal vision, the image in far vision is formed on the retina in the foveal area, but behind the retina for the peripheral vision. Nowadays, it is considered that such a peripheral defocusing causes an elongation of the eye and, consequently, an apparent aggravation of the myopia of the wearer. The documents US 2005/0105047 and WO 2007/041796 propose modifying the optical power of ametropia-correcting unifocal lenses, so that the central area of such a lens is adapted for the foveal vision, and the peripheral area of the lens is adapted for the peripheral vision of the wearer. In this way, the aggravation of the ametropia of the wearer which is due to an inappropriate correction for the peripheral vision is reduced. Furthermore, the document WO 2007/041796 indicates that the size of the central area, which is adapted for the foveal vision, can be personalized for each wearer of lenses, according to his behavior in favoring movements of the eyes and/or the head.
Moreover, it has been observed that some children focus inaccurately when they observe an object which is situated a short distance away, that is to say, in near vision conditions. Because of this focusing defect on the part of a myopic child which is corrected for his far vision, the image of an object close by is also formed behind his retina, even in the foveal area. To avoid making a contribution to the aggravation of the myopia which is due to this focusing defect, it is known to use a myopia-correcting lens which is of the progressive lens type. Such a lens comprises a far vision area, in which the optical power of the lens is adapted to correct the myopia of the wearer when observing a distant object, a near vision area, in which the myopia correction is reduced, and an intermediate area which is situated between the far vision and near vision areas, and in which the optical power of the lens varies continually. Such progressive ophthalmic lenses are adapted for the foveal vision of the weaver.
Nevertheless, it has been observed that each of these two types of ophthalmic lenses, with an area adapted for the peripheral vision on the one hand or even progressive on the other hand, causes more residual aggravation of the ametropia of the wearer.